We Keep Coding

Running Java command including all JARs in current folder

I have just shifted back from an IDE to Notepad to write a Java program. The program is using 20 JARs. I compiled successfully. When I decided to run the Java class file using
java -cp ".\\*" MyProgram
it was giving the standard error "Couldn't find or load main class....".
I was confused because when I used to run the java command with all files in an existing folder, it would just get those JARs as the current folder is already in the classpath. As the program is running from the current folder, I tried using -cp "." to include it explicitly in the classpath but that didn't work either.
Finally I was able to run the program with this command:
java -cp ".\\*;." MyProgram.java
I am asking this question to understand the actual logic behind Java's classpath.
Correct me if I am wrong, but I think that the JAR is just a standard archive in which all the packages are encapsulated in respective folders. If all the JARs are in my current folder including my main class file then why can't I run it with:
java -cp "." MyProgram
or simply:
java MyProgram
If the problem is with the multiple JAR files to include and that's why we used ".\\*" to include all the JARs in the classpath, then why do we have to explicitly include the current folder again in the classpath using:
java ".\\*;." MyProgram

To include all jar required to run your program in command prompt use wildcard *:
java -classpath E:\lib\* HelloWorld
You are using "." that defines current directory and "./*" defines all files in current directory.

The class path is a list of jar files and directories containing the classes and resources of your program. Mentioning a jar file adds its contents to the class path.
"./*" will get you only the jar files in the current directory, "." adds the current directory to the class path. This allows to access all classes (and the jar files as raw file resources but not its contents, i.e. the classes contained in them).
If you need both in the class path, you have to specify both.

You've answered your own question, sort of.
. means that it will look for .class files in the current directory.
JARs act just like a directory. So to have the abc.jar "directory" you would specify abc.jar in your classpath.
If you need both the .class files present in the current directory, and the .class files packaged into JARs found in the current directory, you would have the following classpath: -cp ".:*.jar
All the answers here are telling you to use the wildcard without extension (* or ./*) but this is a bad practice, you don't want Java to go look into irrelevant files, so specify the extension: *.jar.

"." means current directory not files in the directory
"./*" means all files in current directory.
So you want to use all jars in current directory so 2nd will work

Compiling Java package throws errors for external Jars

Pretty basic problem here. So I have a Java package that I have created that has three classes (one has the main method). I am trying to use a few Apache Jars, and have added these to my build path in Eclipse. However Eclipse wont let me build and run it properly, so I am trying the command line. I have added the env var CLASSPATH and pointed it to my lib directory which hold the Apache Jars. However, when I try to use javac I get a bunch of errors:
package org.apache.xmlrpc does not exist
import org.apache.xmlrpc.client.XmlRpcClient;
I was reading the man page for javac and it said that:
If neither CLASSPATH, -cp nor -classpath is specified, the user class path consists of the current directory.
So I tried copying the Jars to the same location as my three source files, but no change.
Can someone please tell me what I'm doing wrong?
Thanks.

Classpath variable (or command line option of javac) must contain all jars explicitly. It cannot go through jar files stored in specified directory.

You can compile this by specifying the option -cp on the command line:
javac -cp foo.jar:bar.jar foo/bar/Baz.java
You then run it with the same option:
java -cp foo.jar:bar.jar foo.bar.Baz

It sounds like you've just set the classpath to the directory containing the jar files. You need to set it to the individual jar files, or use java.ext.dirs to set an "extension" directory containing jar files. I'd recommend using the specific jar files. Something like:
// Assuming Windows...
CLASSPATH = c:\libs\foo.jar;c:\libs\bar.jar
I'd also personally recommend specifying the classpath on the command line instead of using an environment variable - the latter will work, but it ends up being a bit more fiddly if you want to compile different projects against different libraries.
However, I'd actually recommend getting Eclipse working first, rather than retreating to the command line. It should be fine - if you could give us more information about what's failing in Eclipse, we may be able to help you with that instead.

The jar files in the current directory are not automatically included; that only refers to .class files in normal package/directory hierarchy. Jar files must be added either explicitly, or via a wildcard like javac -cp ./* (Assuming JDK6+)
(Some OSes may require an escape of the * to avoid globbing; OSX does not.)

I agree with previous answers, but I would also recommend to use proper java build tool - like ant (perceived easier to use, but not necessary) or maven ( perceived more difficult to use, but really worth learning )

where to place jar in order to run a program from command-line?

this will sound silly but i am executing my code from command prompt and have to use a jar in my class.
I have placed my jar in lib folder of JDK..
but i am still getting error of file not found
any explanation??
EDITED : guys tried all but still not working
EDIT 2 :i am trying to work as was told by this link i am using js-1.6R5.jar
Edit 3 : i undestand all the things you ppl have told but nothing working for me.. pls give me a link to upload my example that i can share with you all.
Edit 4 : i am fed up by setting classpaths but its not working... i have SDK installed in my system, do i need an extra JDK to run my programs from command prompt??

You need to add the jar to the class path by doing the following...
java -classpath D:\myprogram;D:\myprogram\lib\supportLib.jar org.mypackage.HelloWorld
Please see Wikipedia - Classpath_(Java)

You can place it anywhere, as long is you include it in your classpath. See Setting the Class Path for how to include jars in the classpath.
Have in mind that adding something in the JDK lib is almost never a good idea.

You can make a lib folder in your application's directory and put jar files there, then make your application find them by adding lib to your application's classpath.
And, don't put your jar files in JDK's lib folder. It's not good practise.

You need to let Java know that you want to include the jar in your classpath (the list of folders and jars it checks for classes). One way to do this is with the -cp command line argument, something like
java -cp ".;pathToMyJar\myJar.jar" MyClass
Another is to edit the CLASSPATH environment variable in your OS to include your jar.

A simple solution will be to place the jar fiel inside the windows folder if you are doing it in a Windows machine.

Unfortunately your question contains a lot of question signs and few information.
If you are using java.io.File to open jar as a regular file this jar should not be in lib directory. You just have to provide correct path in file system.
If however you are just trying to use jar as a part of your application it should be in classpath. Use either command line java -cp myjar.jar MyMainClassor put full path to this jar to global environment variableCLASSPATH`.

Java - Difficulty installing program from 3 separate .jar files (involves CLASSPATH)

I'm having a little trouble running some Java code, which requires three .jar files to be used. I'm at a lost as to what to do with them--I've tried setting the CLASSPATH (and following the instructions for how to do so in the readme files), but to no avail.
I was wondering if someone could walk me through it? I'd imagine three .jar files would be an easy install for someone who knows what they're doing.
If it helps, I'm using Ubuntu pretty much right out of the box (but I do have JDK and Eclipse installed!)
Runtime library: http://cogcomp.cs.illinois.edu/download/software/20
Additional .jar needed: http://cogcomp.cs.illinois.edu/download/software/23
Program I ultimately need to run: http://cogcomp.cs.illinois.edu/download/software/26
If you're willing to help, I can't thank you enough--you deserve a million kudos!
G

Those are all JAR files. When you execute a JAR file by doubleclicking or using java -jar, the CLASSPATH environment variable and the -cp and -classpath arguments are ignored. The classpath should be defninied in META-INF/MANIFEST.MF file of the JAR. In this particular case, only the second and third JAR have a Class-Path entry in the manifest file:
Class-Path: LBJ2Library.jar
Which is the first JAR. The classpath is telling that it is expecting the LBJ2Library.jar to be in the same folder as the JAR you'd like to execute (either the second or third one).
So, just drop them all in the same folder and execute by java -jar LBJPOS.jar.

If you are using java -jar to run your jar files, then the CLASSPATH variable is ignored. If you are using java -jar, you have two options:
Combine the three jars into one jar.
Run the main class directory and don't use -jar.

Use of the CLASSPATH environment variable is generally discouraged nowadays. This is how it's done (on Linux):
java -cp library1.jar:library2.jar:mainapp.jar <fully qualified name of main class>

You need to set the CLASSPATH .place all the 3 jars in a folder , name it as lib
See below to set classpath
set CLASSPATH=%CLASSPATH%:lib;

How to use a wildcard in the classpath to add multiple jars? [duplicate]

This question already has answers here:
Including all the jars in a directory within the Java classpath
(25 answers)
Closed 4 years ago.
I have been using so many 3rd party libraries(jar files) that my CLASSPATH is completely messed up as i have to include the path for every single jar file that i use.
I've been wondering if there is a way to include all the jar files in a folder using wildcard(*) operator (like *.jar). But it seems to be not working. Is there any other way that can shorten the CLASSPATH that currently looks like an essay ;) on my PC?.

From: http://java.sun.com/javase/6/docs/technotes/tools/windows/classpath.html
Class path entries can contain the basename wildcard character *, which is considered equivalent to specifying a list of all the files in the directory with the extension .jar or .JAR. For example, the class path entry foo/* specifies all JAR files in the directory named foo. A classpath entry consisting simply of * expands to a list of all the jar files in the current directory.
This should work in Java6, not sure about Java5
(If it seems it does not work as expected, try putting quotes. eg: "foo/*")

This works on Windows:
java -cp "lib/*" %MAINCLASS%
where %MAINCLASS% of course is the class containing your main method.
Alternatively:
java -cp "lib/*" -jar %MAINJAR%
where %MAINJAR% is the jar file to launch via its internal manifest.

Basename wild cards were introduced in Java 6; i.e. "foo/*" means all ".jar" files in the "foo" directory.
In earlier versions of Java that do not support wildcard classpaths, I have resorted to using a shell wrapper script to assemble a Classpath by 'globbing' a pattern and mangling the results to insert ':' characters at the appropriate points. This would be hard to do in a BAT file ...

If you mean that you have an environment variable named CLASSPATH, I'd say that's your mistake. I don't have such a thing on any machine with which I develop Java. CLASSPATH is so tied to a particular project that it's impossible to have a single, correct CLASSPATH that works for all.
I set CLASSPATH for each project using either an IDE or Ant. I do a lot of web development, so each WAR and EAR uses their own CLASSPATH.
It's ignored by IDEs and app servers. Why do you have it? I'd recommend deleting it.